Process Applications:

The SierraTherm XR Series furnace is designed specifically for in-line diffusion of phosphorous dopant into silicon wafers used for solar cells. Precision machined and driven ceramic rollers transport wafers through a high temperature profile previously performed in batch or conveyor belt ovens. The XR Series excels in thermal processing for which metal contamination is a critical factor. This includes process profiles from 100 °C to 1000 °C.

Advantages

Ceramic Rollers:

Transportation of wafers with ceramic rollers replaces the traditional metal conveyor belt in the diffusion process. The heated process chamber is now completely metal-free and in-line which is ideal for phosphorous drive-in. In-line processing minimizes handling which can improve yields and process flow. Precision speed control and roller alignment insure uniformity of cell movement.

IR Lamps:

The XR Series uses tungsten filament infrared lamps as the primary heat source, which improves drive-in characteristics with short wavelength heat. The IR lamps provide dramatically rapid response and heat up to diffusion temperature minimizing production down-time. The IR lamp quartz envelope structure also protects filaments from acidic processing environments and isolates them from the furnace's metal-free interior.

Small Footprint:

The XR Series can substantially reduce process floor-space requirements. Extremely rapid heating and cooling rates can be achieved in SierraTherm's roller hearth furnace as only the parts in process need to be heated and cooled. This is unlike batch ovens in which surrounding materials (insulation, boats, etc.) must be heated, and belt furnaces which must heat and cool the conveyor belt along with the parts. The XR Series is also capable of processing parts at higher temperatures than comparable conveyor belt furnaces which can improve diffusion rates. This, combined with rapid heating and cooling, can shorten overall system length dramatically.

Energy Efficiency:

The XR Series is an energy efficient addition to any production line. High mass metal conveyor belts that waste heating and cooling energy in the diffusion cycle have been completely eliminated. IR lamps are able to rapidly change temperature, allowing idling of the furnace to low temperature while not actively processing, thereby saving energy costs. In addition, the XR Series includes an ultra-clean low-mass refractory heating chamber which effectively limits external heat loss. The metal free, low mass ceramic fiber IR Lamp configuration also minimizes time between recipe changes.

Proven SierraTherm Control:

Included as standard equipment on the XR Series is the powerful and convenient Windows based MicroTherm furnace control, profiling, and monitoring system. First developed and introduced by SierraTherm in 1992, today's version is based on many years of furnace experience and customer input. This experience has also resulted in the creation of our precision IR lamp phased power control system which maximizes process temperature stability.